Ligand binding to heme proteins. An evaluation of distal effects.

Mims, Martha P.; Porras, Arturo G.; Olson, John S.; Noble, Robert W.; Peterson, Jim

doi:10.1016/s0021-9258(17)43848-8

Cited by 130 publications

(90 citation statements)

References 50 publications

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“…The equilibrium constant for DIMPI binding to myoglobin is 7.6 x 105 M-1, which is much less than the value (1 x 108 M-1) reported by Wood et al (1987) The ratio of KDImPI/KE for myoglobin is only 3.5 compared with that for the model which is KDIMPI/KEIC = 11, which would indicate that DIMPI is being sterically hindered. To evaluate the extent of the steric effect, standard free energies of binding were analysed by a more recent method of Mims et al (1983). Mims et al (1983) evaluated the extent of steric interaction between the alkyl isocyanide and protein in haem proteins by considering the differences between the free energies of ligand binding to a sterically unconstrained chelated protohaem model in a soap micelle and to the haem protein according to the following expression:…”

Section: Discussionmentioning

confidence: 99%

“…To evaluate the extent of the steric effect, standard free energies of binding were analysed by a more recent method of Mims et al (1983). Mims et al (1983) evaluated the extent of steric interaction between the alkyl isocyanide and protein in haem proteins by considering the differences between the free energies of ligand binding to a sterically unconstrained chelated protohaem model in a soap micelle and to the haem protein according to the following expression:…”

Section: Discussionmentioning

confidence: 99%

“…The myoglobin-CO complex was then titrated with a DIMPI stock solution using a 25 ,l gas-tight syringe with a repeating dispenser attachment. The isocyanide binding constant was calculated from KobS, and the reported binding constant for CO to myoglobin (Mims et al, 1983) as described above for isocyanide binding to model haem complexes.…”

Section: Ligand Binding To Im-haem Solutionsmentioning

confidence: 99%

“…Alkyl isocyanides with alkyl groups of different size have been used as probes for assessing the steric accessibility of the haem iron in haemoproteins (St. George & Pauling, 1951; Ainsworth et al, 1960;Brunori et al, 1972;Stetzkowski et al, 1979;Reisberg & Olson, 1980a-c;Mims et al, 1983). Differences in the binding constants of alkyl isocyanides to a model haem complex in detergent micelle and haemoproteins have also indicated a partitioning effect of the hydrophobic haem environment on binding (Olson et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

“…Results obtained from model studies in toluene and detergent showed no electronic effect and a difference in the partitioning effect of only 11-fold between DIMPI and EIC. Based on these observations, the equilibrium binding constant for DIMPI to myoglobin has been re-measured and the effect of the protein on the free energy of binding re-calculated by a more recent method of analysis (Mims et al, 1983).…”

Section: Introductionmentioning

confidence: 99%

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Alkyl and aromatic isocyanide binding to haem complexes

Patel

Kassner

1989

Biochemical Journal

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Equilibrium constants for the binding of ethyl (EIC), n-butyl (BIC), p-toluenesulphonylmethyl (TMIC) and 2,6-dimethylphenyl isocyanides (DIMPI) to an imidazole-haem complex in toluene and aqueous detergent micelle solutions were determined. In contrast to an earlier study, which indicated that the large affinities of myoglobin for binding DIMPI and 2,6-diethylphenylisocyanide (DEPI) relative to EIC were due to an electronic effect, the present study shows a similarity in binding constants for EIC, BIC, and DIMPI to the imidazole-haem complex in toluene, suggesting no such electronic effect is present. The measured hydrophobic effect (KDIMPI/KEIC = 11) cannot account for the large binding constant reported for DIMPI relative to the binding of EIC to myoglobin. Based on the results of these model studies, the equilibrium binding constant for DIMPI to myoglobin has been re-measured and the standard free energy of binding has been analysed by a more recent method.

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Section: Discussionmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

Section: Ligand Binding To Im-haem Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Alkyl and aromatic isocyanide binding to haem complexes

Patel

Kassner

1989

Biochemical Journal

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The Thermochemistry and Energetics of Organoiron Compounds

Liebman

Slayden

2014

Patai's Chemistry of Functional Groups

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The current study concerns the thermochemistry and energetics of organoiron compounds that contain an iron–carbon bond. The main quantities that are discussed are enthalpies of formation and bond energies. The chapter begins with the simplest binary iron carbides and then considers progressively larger neutral and ionic organic ligands. Within the context of small ligands, binding to iron as found in hemes and hemoglobin is discussed. The acidity and basicity of iron‐containing compounds is also included.

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Application of molecular dynamics and free energy perturbation methods to metalloporphyrin‐ligand systems ii: Co and dioxygen binding to myoglobin

Lopez

Kollman

1993

Protein Science

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The protein contribution to the relative binding affinity of the ligands CO and O2 toward myoglobin (Mb) has been simulated using free energy perturbation calculations. The tautomers of the His E7 residue are different for the oxymyoglobin (MbO2) and carboxymyoglobin (MbCO) systems. This was modeled by performing two‐step calculations that mutate the ligand and mutate the His E7 tautomers in separate steps. Differences in hydrogen bonding to the O2 and CO ligands were incorporated into the model. The O2 complex was calculated to be 2–3 kcal/mol more stable than the corresponding CO complex when compared to the same difference in an isolated heme control. This value agrees well with the experimental value of 2.0 kcal/mol. In qualitative agreement with experiments, the Fe‐C‐O bond is found to be bent (θ = 159.8°) with a small tilt (ϕ = 6.2°). The contributions made by each of the 29 residues — within the 9.0‐Å radius of the iron atom — to the free energy difference are separated into van der Waals and electrostatic contributions; the latter contributions are dominant. Aside from the proximal histidine and the heme group, the residues having the largest difference in free energy in mutating MbO2 → MbCO are His E7, Phe CD1, Phe CD4, Val E11, and Thr E10.

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Ligand binding to heme proteins. An evaluation of distal effects.

Cited by 130 publications

References 50 publications

Alkyl and aromatic isocyanide binding to haem complexes

Alkyl and aromatic isocyanide binding to haem complexes

The Thermochemistry and Energetics of Organoiron Compounds

Application of molecular dynamics and free energy perturbation methods to metalloporphyrin‐ligand systems ii: Co and dioxygen binding to myoglobin

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